The present invention relates to angiography and more specifically, injectors used to inject a medical fluid such as radiographic material into living organisms.
One of the major systems in the human body is the circulatory system. The major components of the circulatory system are the heart, blood vessels, and the blood, all of which are vital to the transportation of materials between the external environment and the different cells and tissues of the human body.
The blood vessels are the network of passageways through which the blood travels in the human body. Specifically, arteries carry the oxygenated blood away from the left ventricle of the heart. These arteries are aligned in progressively decreasing diameter and pressure capability from the aorta, which carries the blood immediately out of the heart to other major arteries, to smaller arteries, to arterioles, and finally to tiny capillaries, which feed the cells and tissues of the human body. Similarly, veins carry the oxygen-depleted blood back to the right atrium of the heart using a progressively increasing diameter network of venules and veins.
If the heart chambers, valves, arteries, veins or other capillaries connected thereto are either abnormal (such as from a birth defect), restricted (such as from atherosclerotic plaque buildup), or deteriorating (such as from aneurysm formation), then a physician may need to examine the heart and connected network of vessels. The physician may also need to correct any problems encountered during the examination with a catheter or similar medical instrument.
Angiography is a procedure used in the detection and treatment of abnormalities or restrictions in blood vessels. During angiography, a radiographic image of a vascular structure is obtained by injecting radiographic contrast material through a catheter into a vein or artery. The vascular structures fluidly connected with the vein or artery in which the injection occurred are filled with contrast material. X-rays are passed through the region of the body in which the contrast, material was injected. The X-rays are absorbed by the contrast material, causing a radiographic outline or image of the blood vessel containing the contrast material. The x-ray images of the blood vessels filled with contrast material are usually recorded onto film or videotape and are displayed on a fluoroscope monitor.
Angiography gives the doctor an image of the vascular structures in question. This image may be used solely for diagnostic purposes, or the image may be used during a procedure such as angioplasty where a balloon is inserted into the vascular system and inflated to open a stenosis caused by atherosclerotic plaque buildup.
Currently, during angiography, after a physician places a catheter into a vein or artery (by direct insertion into the vessel or through a skin puncture site), the angiographic catheter is connected to either a manual or an automatic contrast injection mechanism.
A simple manual contrast injection mechanism typically has a syringe and a catheter connection. The syringe includes a chamber with a plunger therein. Radiographic contrast material is suctioned into the chamber. Any air is removed by actuating the plunger while the catheter connection is facing upward so that any air, which floats on the radiographic contrast material, is ejected from the chamber into the air. The catheter connection is then attached to a catheter that is positioned in a vein or artery in the patient.
The plunger is manually actuated to eject the radiographic contrast material from the chamber, through the catheter, and into a vein or artery. The user of the manual contrast injection mechanism may adjust the rate and volume of injection by altering the manual actuation force applied to the plunger.
Often, more than one type of fluid injection is desired, such as a saline flush followed by the radiographic contrast material. One of the most common manual injection mechanisms used today includes a valve mechanism which controls which of the fluids will flow into the valving mechanism and out to the catheter within the patient. The valve mechanism contains a plurality of manual valves that the user operates manually to open and close that particular fluid channel. When the user suctions or injects contrast fluid into the chamber, the fluid is pulled from the valve mechanism via the open valves. By changing the valve positions, another fluid may be injected.
These manual injection mechanisms are typically hand actuated. This allows user control over the quantity and pressure of the injection. However, all of the manual systems are only capable of injecting the radiographic contrast material at maximum pressure that can be applied by the human hand (i.e., 150 p.s.i). Also, the quantity of radiographic contrast material is typically limited to a maximum of about 12 cc. Finally, there are no safety limits on these manual contrast injection mechanisms which act to restrict or stop injections that are outside of reasonable parameters (such as rate or pressure) and no active sensors to detect air bubbles or other hazards.
Currently used motorized injection devices consist of a syringe connected to a linear actuator. The linear actuator is connected to a motor, which is controlled electronically. The operator enters into the electronic control a fixed volume of contrast material to be injected at a fixed rate of injection. The fixed rate of injection consists of a specified initial rate of flow increase and a final rate of injection until the entire volume of contrast material is injected. There is no interactive control between the operator and machine, except to start or stop the injection. Any change in flow rate must occur by stopping the machine and resetting the parameters.
The lack of ability to vary the rate of injection during the injection results in suboptimal quality of angiographic studies. This is because the optimal flow rate of injections varies considerably between patients. In the cardiovascular system, the rate and volume of contrast injection is dependent on the size of and blood flow rate within the chamber or blood vessel being injected. In many or most cases, these parameters are not known precisely. Moreover, the optimal rate of injection can change rapidly, as the patient""s condition changes in response to drugs, illness, or normal physiology. Consequently, the initial injection of contrast material may be insufficient in flow rate to outline the structure on x-ray imaging, necessitating another injection. Conversely, an excessive flow rate might injure the chamber or blood vessel being injected, cause the catheter to be displaced (from the jet of contrast material exiting the catheter tip), or lead to toxic effects from contrast overdose (such as abnormal heart rhythm).
Furthermore, the linear actuator is usually connected to the plunger by a xe2x80x9csnap fitxe2x80x9d arrangement wherein automatic engagement and disengagement of the plunger with the linear actuator is desirable to prevent contamination of the pumping chamber of the syringe and to simplify the operation of the injection system. In some situations, it is desirable to damage or destroy the connection portion of the plunger to prevent reuse of the syringe. As a result, particulates may remain in the connection area and cause problems during subsequent interconnections.
Another problem often encountered when providing a syringe plunger arrangement which automatically engages and disengages with the linear actuator is that the force necessary for engagement is too high, while the force necessary for disengagement is too low. With such an arrangement, it may be difficult to maintain the plunger in a fixed position relative to the pumping chamber because the plunger may be driven forward during the engagement procedure, and it may be difficult to maintain the plunger in an engaged position with the linear actuator when the linear actuator is retracted.
At present, the operator can choose between two systems for injecting contrast material: a manual injection system which allows for a variable, operator interactive flow rate of limited flow rate and a preprogrammed motorized system without operator interactive feedback (other than the operator can start/stop the procedure).
The present invention provides a number of devices and methods for releasably connecting a syringe plunger to a drive member of an angiographic injector of a type having a syringe holder. A syringe includes a syringe body having a distal end and a proximal end, and the syringe body defines a pumping chamber. The syringe plunger is located in the pumping chamber and is adapted for reciprocal motion. An actuating shaft is coupled to the syringe plunger and is movable through the syringe body to control movement.
In one embodiment of the present invention, a syringe plunger includes a capture member projecting outwardly in a proximal direction, while an actuating shaft includes a circumferential groove. A latch is disposed on an inner surface of the capture member, and a finger extends radially outwardly from the capture member. During the connecting procedure, the actuating shaft is driven forward to contact the syringe plunger, and the capture member flexes radially outwardly and engages with the circumferential groove to form a releasable connection. A release actuator is disposed proximal to the syringe body. The release actuator may be a plate defining an aperture for allowing manipulation of the syringe plunger. During the disconnecting procedure, the syringe plunger is retracted such that the finger abuts against an inner surface of the plate and causes the capture member to flex radially outwardly. The latch disengages with the circumferential groove and the syringe is disconnected from the actuating shaft. In the exemplary embodiment, the capture members are designed to permanently deform during the disconnecting procedure to ensure that the syringe is disposed of after use with one patient and not accidentally re-used on a new, different patient.
In another embodiment of the present invention, a syringe plunger includes a circumferential groove, and an actuating shaft includes a pivot member for capturing the syringe plunger. The pivot member is disposed at a distal portion of an actuating shaft. A distal portion of the pivot member includes a latch projecting outwardly from an inner surface thereof, and a proximal portion of the pivot member includes a ramped lug projecting outwardly from an outer surface thereof. A release actuator may be a plate located proximal to the syringe body defining an aperture for allowing manipulation of the syringe plunger. During the connecting procedure, the actuating shaft is driven forward to contact the syringe plunger, the distal portion of the pivot member projects radially outwardly, and the latch engages with the circumferential groove to form a releasable connection. During the disconnecting procedure, the syringe plunger is retracted such that the ramped lug slidingly engages with a sidewall of the aperture. The proximal end of the pivot member is driven radially inwardly and the distal end of the pivot member is projected radially outwardly such that the latch disengages with the circumferential groove.
In another embodiment, a syringe plunger is magnetically connected to an actuating shaft. The syringe plunger includes a first insert comprising a ferrous metal, permanent magnet, or electromagnet, while the actuating shaft includes a second insert comprising a ferrous metal, permanent magnet, or electromagnet. Any combination of ferrous metal, permanent magnet or electromagnet may be used when configuring the first and second insert as long as a permanent magnet or electromagnet is included in one of the inserts. During the connecting procedure, the actuating shaft is driven forward to contact the syringe plunger, and the syringe plunger remains magnetically attached to the actuating shaft. One of the benefits of utilizing a magnetic syringe plunger arrangement is that a xe2x80x9czeroxe2x80x9d engagement force is required. As described in the previous embodiment, a release actuator is disposed proximal to the syringe body. The release actuator may be a plate located proximal to the syringe body, and the plate defines an aperture for allowing manipulation of the syringe plunger. The syringe plunger further includes a base having an outer diameter larger than the aperture of the plate. During the disconnecting procedure, the syringe plunger is retracted until the base abuts against an inner surface of the plate. Upon further retraction, the plunger disengages from the actuating shaft.
In another embodiment, a syringe plunger is attached to an actuator having a split collet actuator head. The syringe plunger includes a plunger support member having a receiving aperture formed therein, and at least one retaining member located thereon. The split collet actuator head comprises an alignment shaft positioned between a first collet member and a second collet member. The individual collet members have flange portions formed thereon. Biasing members are positioned between the first and second collet members and bias the collet members outwardly. During the connecting procedure, the actuating shaft is driven forward to contact the syringe plunger, wherein the first and second collet members are forced inwardly. Thereafter, the at least one retaining member engages the individual flange members formed on the collet members and the biasing members force the first and second collet members outwardly. Thereafter, the syringe plunger is coupled to the actuating shaft.
To detach the syringe plunger from the actuator the actuator is retracted to a position proximal the rear plate of the syringe holder assembly. During the retraction procedure, the detachment members located on the first and second collet members are caused to engage the rear plate of the syringe holder assembly. As a result, the first and second collet members are forced inwardly and the at least one retaining member disengages the flange portion. Upon further retraction, the plunger disengages from the actuating shaft.
Other objects, features, and advantages of the present invention will become apparent from a consideration of the following detailed description and from the accompanying descriptions.